This invention relates in general to a retractable cargo height sensing system for sensing when cargo on a cargo transporting vehicle is above or below a predetermined distance above the roadway and provides an alarm when the cargo is above that distance.
It is well recognized in the field of cargo transporting vehicles that when the cargo being transported is above a predetermined distance above the roadway, the cargo will impact bridges and the like when it is above the predetermined distance. In the example of transporting a number of vehicles, such as cars or vans, cargo transporting vehicles having a tractor and a trailer are known and have a wide variety of configurations and designs. In general, the trailer has a number of vehicle carrying platforms that are movable by hydraulic cylinders. The vehicles are driven onto the platforms and the platforms are then moved by hydraulic cylinders into a nested position so the vehicles are nested into a compact configuration to decrease the height that the vehicles are carried. When the vehicles are in the proper position, pins are inserted in support members adjacent the hydraulic cylinders so that the weight of the vehicle is supported by the support members and fluid pressure need not be applied to the hydraulic cylinders to support the vehicles while they are being transported.
Roadways have various obstructions, such as bridges, that are designed to allow a height clearance of a predetermined distance above the roadway, such as 13 ft, 7 inches or another predetermined distance. Other obstructions include wires passing across the roadway and trees growing along the road with their branches over the road trimmed to a predetermined height. These other obstructions are likewise designed or trimmed to a predetermined height. Accordingly, a cargo transporting vehicle can travel along the roadway so long as the cargo is not higher than the predetermined distance. If the cargo is higher it will hit the bridge, tree, or wires or other obstruction causing damage to both the obstruction and the cargo.
One known approach to check the height of the cargo is to measure, with a stick, the height of cargo after it is believed to be at the correct height with the vehicles properly nested. If it is observed that the cargo is above the predetermined distance, it must be a readjusted so that it is below. This approach is cumbersome and inaccurate since generally the predetermined distances are in the order of magnitude of 13 to 14 feet and the driver has difficulty in checking height of the cargo.
Another known system works on the principal of lack of pressure in the hydraulic system that moves the hydraulic cylinders to move the platforms on the trailer. In this system, pressure is sensed in the hydraulic cylinders and anytime there is a buildup of hydraulic pressure in the system, the driver will receiving alarm alerting the driver that a vehicle platform or deck is up. The problem with this system is that drivers set the vehicle platform or attach the post pins while loading and unloading and accordingly sensing hydraulic pressure in the hydraulic cylinders does not assure that the cargo is within the predetermined height from the roadway.
It is desirable to provide a cargo height sensing system for sensing whether cargo on a cargo transporting vehicle is below a predetermined distance above the road. Such a system allows the driver of the cargo transporting vehicle assurance that the cargo can pass under obstructions above that height. It is also desirable that such a system provide an alarm which is activated when the cargo is above the predetermined distance so that the driver can lower the cargo before commencing his journey and deactivated when the cargo is below the predetermined height.
Another desirable feature of a cargo height sensing system is that the sensors detecting the height of the cargo are retractable from a raised position, which may be above the predetermined distance, to a lowered position below the predetermined distance or height. This retractable feature avoids damage to the sensors from impacting its obstructions in the roadway during movement of the cargo transporting vehicle.
It is another desirable feature of a cargo height sensing system to move the sensors from the lower position to the raised position when a power takeoff unit (PTO) of the cargo transporting vehicle is activated and its brake system is activated. The first requirement, that a power takeoff unit may be engaged, provides that pressurized fluid is provided to the hydraulic cylinders to raise a lower the cargo carrying platforms or deck. By also requiring that the brakes on the cargo transporting vehicle be activated before raising the sensors, any movement of the cargo carrying vehicle is impeded when raising the sensors. Such a system allows for raising the sensors only when the proper conditions exist and vehicles may be loaded onto the cargo transporting vehicle.
After vehicles are mounted on a cargo transporting vehicle is desirable to lower the sensors for moving the cargo transporting vehicle. Accordingly, is desirable to lower the sensors when the brake system is released and the power takeoff unit is disengage. In this condition, the hydraulic cylinders which raise and lower the cargo do not have pressurized hydraulic fluid supplied them and cannot move the cargo and when releasing the brake system the vehicle is free to move.